#include<bits/stdc++.h>
using namespace std;
#define pb push_back
#define fi first
#define se second
#define mp make_pair
#define all(a) a.begin(),a.end()
#define sz(a) (int)(a.size())
#define lb lower_bound
#define ub upper_bound
#define owo ios_base::sync_with_stdio(0);cin.tie(0);
#define MOD (ll)(1e9+7)
#define INF (ll)(1e18)
#define debug(...) fprintf(stderr, __VA_ARGS__),fflush(stderr)
#define time__(d) for(long blockTime = 0; (blockTime == 0 ? (blockTime=clock()) != 0 : false);\
debug("%s time : %.4fs\n", d, (double)(clock() - blockTime) / CLOCKS_PER_SEC))
typedef long long int ll;
typedef long double ld;
typedef pair<ll,ll> PII;
typedef pair<int,int> pii;
typedef vector<vector<int>> vii;
typedef vector<vector<ll>> VII;
struct slope{
multiset<ll>s;
ll m=0,c=0;
slope(){}
slope(ll _m,ll _c ,ll x){
m = _m;
c = _c;
s.insert(x);
s.insert(x);
}
void merge(const slope &t){
m+=t.m;
c+=t.c;
for(ll z:t.s)s.insert(z);
}
void upd(ll k){
while(m>1){
auto it = s.end();
it--;
m--;
c+=*it;
s.erase(it);
}
auto it = s.end();
it--;
ll a = *it+k;
s.erase(it);
it = s.end();
it--;
ll b = *it+k;
s.erase(it);
s.insert(a);s.insert(b);
c-=k;
}
};
const int MAXN = 3e5+1;
vii adj(MAXN);
vector<ll>w(MAXN);
vector<slope>dp(MAXN);
void dfs(int v){
if(!sz(adj[v]))dp[v] = slope(1,-w[v],w[v]);
for(int x:adj[v]){
dfs(x);
if(sz(adj[x]))dp[x].upd(w[x]);
}
for(int x:adj[v]){
if(sz(dp[x].s) > sz(dp[v].s)){
swap(dp[x].s,dp[v].s);
swap(dp[x].c,dp[v].c);
swap(dp[x].m,dp[v].m);
}
dp[v].merge(dp[x]);
}
/*
cout<<"node"<<" "<<v<<'\n';
cout<<"container :"<<'\n';
for(int x:dp[v].s)cout<<x<<" ";
cout<<'\n';
cout<<dp[v].m<<" "<<dp[v].c<<'\n';
* */
}
int main()
{
owo
int n,m;
cin>>n>>m;
for(int i=2;i<=n+m;i++){
int p;
cin>>p>>w[i];
adj[p].pb(i);
}
dfs(1);
while(dp[1].m >= 1){
auto it = dp[1].s.end();
it--;
dp[1].m--;
dp[1].c+=*it;
dp[1].s.erase(it);
}
cout<<dp[1].c<<'\n';
}
